1. Field of the Invention
This invention relates to a device for detecting the remaining amount of developer stored in a developer tank, and in particular, to such a device for use with a developing device which uses toner particles for developing an electrostatic latent image.
2. Description of the Prior Art
A developing device for developing an electrostatic latent image formed on an image bearing member, such as a photosensitive member, with toner particles is well known in the art. Such a developing device is commonly used in various types of imaging machines, such as electrophotographic copiers and printers, and it typically includes a developer tank for storing therein a quantity of developer. As the development takes place, the developer stored in the developer tank is consumed, so it is necessary to feed the developer into the tank. In order to indicate to the operator that the necessity to replenish developer arises, use has been made of a device for detecting the amount of remaining developer in the tank. Such a prior art detecting device includes a detector coil disposed inside of the developer tank, which changes its inductance depending on the amount of developer remaining in the tank. However, such a prior art device requires the provision of an electrical circuit for processing a signal picked up from the coil, and, thus, it tends to be complicated in structure and high in cost.